GB2028436A

GB2028436A - Fluid-flow Metering Devices

Info

Publication number: GB2028436A
Application number: GB7834447A
Authority: GB
Original assignee: AGMET INSTR
Current assignee: AGMET INSTR
Priority date: 1978-08-24
Filing date: 1978-08-24
Publication date: 1980-03-05
Also published as: FR2434372A1; FR2434372B3; GB2028436B; DE2934198A1; JPS5558413A

Abstract

A fluid-flow metering device comprises a duct for conveying fluid and means defining an orifice 19 positioned in the duct. The orifice is of convergent form in the direction of fluid flow and a portion of the fluid is forced through the duct under ram effect of constricted fluid flow. A rotor 14 is positioned with respect to the orifice so that fluid emerging under said ram effect impinges upon the rotor to cause rotation thereof. Means are provided for sensing this rotation. <IMAGE>

Description

SPECIFICATION Fluid-flowing Metering Devices Field of the Invention The present invention relates to fluid-flow metering devices.

Summary of the Invention According to the invention there is provided a fluid-flow metering device comprising a duct for conveying fluid to be metered, means defining an orifice positioned in said duct, said orifice having a tapering cross-section to define an axis of taper which is arranged so that when fluid flow in the duct is in the tapering direction of said orifice in the sense that fluid enters the orifice at its least tapered part and exits from is most tapered part, fluid is forced through the orifice under a ram effect of constricted fluid flow, a multibladed rotor arranged for rotation with respect to said orifice so that fluid emerging from said orifice in said tapering direction impinges upon its blades to cause rotation thereof, and means for sensing said rotation of said rotor.

Brief Description of the Drawings Embodiments of the invention will now be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a schematic illustrating a general principle of the invention; Figure 2 is a cross-sectional view through a fluid-flow meter according to one embodiment of the invention; Figure 3 is a view along the direction of arrow A of Figure 2; and Figures 4, 5 and 6 are further embodiments respectively of a fluid-flow metering device according to the invention.

Detailed Description of Preferred Embodiments The fluid-flow metering device as shown in Figure 1 comprises a fluid-flow carrying duct 1 having a longitudinal axis 2. A projecting member 3 defining an orifice 4, transversely positioned with respect to the axis 2 of the duct 1, extends from the internal surface wall of duct 1.

The orifice 4 has a tapering cross-section, the tapering occurring in a direction of fluid flow in the duct 1 represented by arrows B so that in these conditions the most tapered part of the orifice 4 faces downstream. As shown in Figure 1 the axis of the orifice 4 is parallel to the longitudinal axis 2 of the duct 1 and consequently to the fluid flow lines in the duct 1.

A multi-bladed rotor 5 is arranged for rotation in the duct 1. The rotor 5 comprises six radially directed substantially rectangular axiaily extending blades 5a each terminating in a bulbous tip Sb in one or more of which is embedded a small rod of ferrite.

A sensor 6 is mounted to the internal wall of the duct 1 as shown and positioned adjacent the rotor 5. The sensor is adapted to sense rotation of the rotor 4 by electrical coupling between the rods in the tips 5b of the rotor 5. For more detailed information regarding the sensing action between the sensor 6 and rotor 5 reference may be had to U.K. Patent 1 505682.

The rotor 5 is arranged in the duct so that its axis of rotation Sc is spaced from the axis of the orifice 4.

When the tapering direction of orifice 4 is in the direction of flow of fluid B in the duct 1, fluid is forced through the tapering orifice 4 under a ram effect of constricted fluid flow. The fluid which emerges from the orifice 4 by this ram effect impinges on the blades 5a of rotor 5 to effect rotation thereof. This rotation is sensed by the sensor 6.

A more detailed constructional embodiment of a fluid-flow metering device according to the invention is shown in Figures 2 and 3.

The metering device shown in Figures 2 and 3 comprises a fluid-flow carrying duct 7 provided with a port 8. The port 8 is provided with an annular ledge 9 delimiting a threaded entrance portion 10 of the port 8. The duct 7 has respective internally threaded ends 11 to permit extension ducts (not shown) to be connected thereto.

A body 12 is detachably mounted in the port 8.

The body 12 has an upper part 13 housing a sensor device (not shown) for sensing rotation of a muiti-bladed rotor 14 housed for rotation in a lower part 1 5 of the body 12. The lower part 1 5 is open to the interior of the duct 7.

An annular flange 1 6 of the body 12 lies between the upper and lower parts 13 and 15 of the body 12, and rests on the annular flange 9 with the interposition of an O-ring seal 1 7. With the body 12 located as shown in Figure 2 the assembly is completed by means of a closure cap 1 8 screwably engaging the threaded portion 10 to firmly tighten the body 1 2 upon the O-ring seal 17.

The lower part 15 of body 12 is provided with an orifice 1 9 which has a cross-section tapering in a direction upstream to downstream relative to fluid flowing in the duct in a direction indicated by the arrows C. The axis 1 9a of the orifice 1 9 is parallel to the axis 7a of the duct 7.

The disposition of the rotational axis 1 4a of the rotor 14 and the axis 1 9a of the orifice 1 9 is such that fluid is forced through the orifice 1 9 under the ram effect of constricted fluid flow to impinge on the blades of the rotor 14 to effect rotation thereof. This rotation is sensed by the sensor in the upper part 13 in a manner as fully described in the afore-said U.K. Patent 1 505682.

Alternatively, the body 12 may be formed of two parts, a top part housing the sensing device and the bottom part being in the form of a stainless steel ring positioned so that its axis lies along the axis of the port 8. The stainless steel mounting ring will be provided with an orifice similar to orifice 19 of body 12 shown in Figure 2.

Additionally, it should be observed that the bottom part 1 5 of body 12 shown in Figure 2 may be partly closed off, totally closed off, or left open as shown. In each case exit holes may be provided on the downstream side for egress of fluid after impingement upon rotor 14.

Further embodiments of the fluid-flow metering device of the invention are to be seen in Figures 4 to 6 wherein like component parts as between the arrangement of Figures 2 and 3 and these Figures, will be given the same reference numerals.

In Figures 4 to 6 the rotor 14 is shown positioned outside the fluid flow carrying duct 7 and replaceably mounted therein with means 20 attached thereto defining an inlet and an outlet to the rotor, positioned to be in the duct 7. The inletoutlet means defining a probe part of the metering device, may be inserted into the duct 7 through a ball or gate valve (not shown).

The inlet-outlet means 20 effectively comprises inlet and outlet conduits 21 and 22.

In Figure 4 the outlet conduit 22 is shorter than the inlet conduit 21, while in Figure 5 both conduits have the same length. The outlet conduit 22 may be arranged so that exiting fluid is parallel to general direction of fluid flow as shown.

However this is not essential as exit flow may be transverse to general flow direction if desired. In this case the outlet conduit 22 would end at 22-3 as shown in Figure 4, the wall of outlet means 20 at the point then being indicated by hatched line 20'.

In Figure 6 the conduits are coaxial with the inlet conduit being of smaller cross-section.

In each of Figures 4 to 6 the inlet conduit is provided with an inlet orifice 1 9 of tapering crosssection to provide the ram effect of constricted fluid flow as hereinbefore described. The axis 1 9a of the inlet orifice is parallel to the fluid flow lines and the longitudinal axis of the duct 7 and, of course, fluid flow can be arranged to occur in the duct 7 so that its direction of movement is in the tapering direction of the orifice 19.

The axis of the tapered orifice in the embodiments previously described, has been shown parallel to the longitudinal axis of the fluidflow carrying duct.

This is a preferred form since it is possible for the axis of the orifice to be at any angle up to 600 to the axis of the duct. At any angle within this range therefore it is possible to achieve the ram effect of constricted fluid flow as fluid passes through the orifice in the general direction of its taper, that is to say entering at its least tapered part and exiting at its most tapered part.

Claims

1. A fluid-flow metering device comprising a duct for conveying fluid to be metered, means defining an orifice positioned in said duct, said orifice having a tapering cross-section to define an axis of taper which is arranged so that when fluid flow in the duct is in the tapering direction of said orifice in the sense that fluid enters the orifice at its least tapered part and exits from its most tapered part, fluid is forced through the orifice under a ram effect of constricted fluid flow, a multibladed rotor arranged for rotation with respect to said orifice so that fluid emerging from said orifice in said tapering direction impinges upon its blades to cause rotation thereof, and means for sensing said rotation of said rotor

2.A fluid-flow metering device as claimed in Claim 1 wherein said orifice is positioned in a projecting member transversely positioned in the duct with respect to its longitudinal axis.

3. A fluid-flow metering device as claimed in Claim 2 wherein said projecting member forms part of a housing in which the rotor is mounted for rotation.

4. A fluid-flow metering device as claimed in Claim 3 wherein said housing is part of a body portion containing said sensor means, the body portion being screw mounted to the duct.

5. A fluid-flow metering device as claimed in Claim 4 wherein said housing projects within the duct, said orifice being formed in a wall of the housing.

6. A fluid-flow metering device as claimed in Claim 5 wherein the housing is open at its lower part to the interior of the duct.

7. A fluid-flow metering device as claimed in Claim 4 wherein said housing is located externally of the duct.

8. A fluid-flow metering device as claimed in Claim 7 wherein a block constituting a probe projects from the housing interiorally of the duct, the block or probe having inlet and outlet conduits for fluid in the duct leading to the housing, said inlet conduit being provided with said orifice at its entrance.

9. A fluid-flow metering device as claimed in claim 8 wherein the outlet conduit is shorter than the inlet conduit.

10. A fluid-flow metering device as claimed in Claim 9 wherein the outfall from the outlet conduit is arranged to be transverse to the fluid flow.

11. A fluid-flow metering device as claimed in Claim 9 wherein the outfall from the outlet conduit is arranged to be parallel to the general direction of fluid flow.

12. A fluid-flow metering device as claimed in any one of Claims 8 to 11 wherein the inlet and outlet conduits are coaxial.

13. A fluid-flow metering device as claimed in Claim 12 wherein the inlet conduit is of smaller cross-section than the outlet conduit.

14. A fluid-flow metering device as claimed in any preceding claim wherein the axis of said orifice is parallel to the longitudinal axis of the duct and thus the flow lines of flowing fluid in the duct.

1 5. A fluid-flow metering device as claimed in any one of Claims 1 to 13 wherein the axis of the orifice lies within the range 0 to 600 with respect to the axis of the duct.

1 6. A fluid-flow metering device as claimed in any preceding claim wherein said multibladed rotor comprises six radially directed rectangular blades.

1 7. A fluid-flow metering device as claimed in Claim 1 6 wherein each blade terminates in a bulbous tip in which is embedded a small rod of ferrite.

1 8. A fluid-flow metering device as claimed in Claim 1 7 wherein said sensor means is adapted to sense rotation of the rotor by electrical coupling between said ferrite rods in the tips thereof.

1 9. A fluid-flow metering device substantially as hereinbefore described with reference to the accompanying drawings.